Synthesis, characterisation and supercritical fluid chromatography enantioseparation of new liquid crystalline materials

ABSTRACT

Enantiomeric excess (EE) highly affects the mesomorphic properties of mesogens containing centre of chirality. Thus, there is need of methods for evaluation of the EE of newly synthesised compounds as it should be considered when discussing the mesomorphic properties. We report synthesis and characterisation of ten new racemic mixtures based on (R,S)-3-octanol, which were used to develop an enantioseparation method that can be used for the assessment of the EE of chiral liquid crystals and their mixtures. The compounds vary in the length of the oligomethylene spacer and lateral fluorine substitution of the aromatic core. The mesomorphic properties of novel materials were measured. Supercritical fluid chromatography with polysaccharide-based chiral stationary phases was used to develop reliable method for enantioseparation of the materials. A complete separation of (S) and (R) enantiomers with resolution values higher than 2.0 was obtained for all materials using simple mobile phase. The enantiomer elution order was assessed using pure (S) enantiomers of all materials. For all materials (R) enantiomer elutes first which is advantageous for use as optical purity control of newly synthesised (S) enantiomers.

Graphical Abstract

KEYWORDS:

• Liquid crystal
• synthesis
• racemic mixtures
• enantioseparation
• supercritical fluid chromatography

Acknowledgments

The authors gratefully acknowledge the financial support of the Military University of Technology (project number PBS 23-895), the Czech Science Foundation (project number 20-19655S) and the Charles University (project number SVV260440).

Disclosure Statement

No potential conflict of interest was reported by the authors.

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Funding

This work was supported by the Grantová Agentura České Republiky [20-19655S];Wojskowa Akademia Techniczna (PL) [PBS 23-895];Přírodovědecká Fakulta, Univerzita Karlova [SVV260440].